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WO1996038958A2 - Systeme d'integrite reparti a memoire adressable par le contenu - Google Patents

Systeme d'integrite reparti a memoire adressable par le contenu Download PDF

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Publication number
WO1996038958A2
WO1996038958A2 PCT/EP1996/002334 EP9602334W WO9638958A2 WO 1996038958 A2 WO1996038958 A2 WO 1996038958A2 EP 9602334 W EP9602334 W EP 9602334W WO 9638958 A2 WO9638958 A2 WO 9638958A2
Authority
WO
WIPO (PCT)
Prior art keywords
ports
devices
port
switching
network
Prior art date
Application number
PCT/EP1996/002334
Other languages
English (en)
Other versions
WO1996038958A3 (fr
Inventor
Anne O'connell
Thomas C. Hogan
John Healy
Original Assignee
3Com Ireland
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3Com Ireland filed Critical 3Com Ireland
Priority to AU59026/96A priority Critical patent/AU5902696A/en
Priority to GB9805471A priority patent/GB2322055B/en
Publication of WO1996038958A2 publication Critical patent/WO1996038958A2/fr
Publication of WO1996038958A3 publication Critical patent/WO1996038958A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/44—Star or tree networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/46—Interconnection of networks
    • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
    • H04L12/462—LAN interconnection over a bridge based backbone
    • H04L12/4625—Single bridge functionality, e.g. connection of two networks over a single bridge

Definitions

  • the present invention relates to computer networks and more particularly networks which are usually known as local area networks (LANs).
  • LANs local area networks
  • a bridge or switch contains an up-to-date list of all device addresses and the ports to which those terminals are connected.
  • each bridge For large networks, the network is separated by bridges and switches. Normally each bridge keeps a record in a memory of all ports in the network and the associated MAC addresses. This requires each bridge to have a very large memory. As part of the normal maintenance of the network, it is the practice to "age out" the address of any port and the MAC address of a device connected thereto which is not being used. In this way each CAM of each bridge or switch is kept up to date.
  • a switch will be constructed using a plurahty of functionally identical modules each with a CAM, a plurality of ports for connection to devices and a communication port for transferring data between modules.
  • One of the modules will be provided with an output port for connection to the rest of the network.
  • each module will know which ports and which devices are local to it. Packets for any non-local ports are sent to the communications port. In contrast with normal bridges which learn the ports and addresses of all devices in the network, each module will only learn the port numbers and addresses of all ports which are local to it. All addresses which are non-local will be allocated the port number of the communications port except for the module which is provided with the output port for the rest of the network.
  • FIG. 1 shows diagrammatically a computer network incorporating a number of bridges or structures
  • Fig. 2 shows one embodiment of a bridge or switch according to the present invention
  • Fig. 3 shows a part of the bridge or switch shown in Fig. 2 for explaining the operation thereof.
  • a local area network will be separated up into a number of discrete areas using bridges or switches and that the ports incorporated within one or more areas will be provided as ports on a box which is also provided with its own microprocessor and CAM.
  • a network is assumed to comprise five multi-port bridges or switches 1,2,3 and 4 which are interconnected.
  • Each switch supports a number of devices attached to ports of the switch in a conventional manner. It is common to supply multi-port bridges or switches with a predete ⁇ nined number of ports but problems arise when a user wishes to connect more devices to a bridge than there are ports available. In the past this has required replacing the multi-port bridge with another having a greater number of ports.
  • a multiport bridge or switch be assembled from one or more identical modules and for the sake of this example we will use four identical modules ABCD as shown in Fig. 2 which when connected together in a stack will function as a single bridge or switch as far as the network is concerned and is capable of operating as a switch.
  • Each module is provided with a number of ports to which devices can be connected.
  • Fig. 2 we show that there are ten ports numbered 0-9 for each module for this purpose although it will be noted that port 0 of module A is in fact the port which connects to the rest of the network.
  • Each module is also provided with an additional port 10 which is used as a communications port with access to a local bus 11 so that data can be transferred from module to module within the stack.
  • additional ports can be provided for a bridge or switch simply by supplying one or more modules and connecting them to the data bus 11.
  • each module has a CAM 12 for containing the ports and associated MAC address of all devices which are connected to the stack. It also knows which MAC addresses are its responsibility, being local to itself. In mis embodiment, any MAC address which the CAM and processor have identified as being non-local, is flagged as a "permanent entry".
  • a CAM 12 for containing the ports and associated MAC address of all devices which are connected to the stack. It also knows which MAC addresses are its responsibility, being local to itself. In mis embodiment, any MAC address which the CAM and processor have identified as being non-local, is flagged as a "permanent entry".
  • the MAC address of the device attached to port 4 of box A is in the form 0000010 and that this device wishes to utilize the network by sending a standard ethernet packet which includes a source address, a destination address and data.
  • the processor of box A examines its CAM for the source address but fails to find it. The arrangement is such that in these circumstances the source address and port are "learned" by the CAM with an entry being made in the CAM for the box A.
  • the processor then examines the CAM for the destination address for the packet which it finds. This indicates that the packet must be directed to the communications port 10.
  • the destination of this packet is in fact a device connected to the box B.
  • the packet will be received by the communications port 10 on the box B via the local bus and the processor for the box B will communicate the packet to the appropriate port.
  • the processor will insert the source address of the packet into its CAM 12 together with a flag, which will indicate that the source MAC address is not on a normal port of the box B but is somewhere else having come via the communications port 10. This flag will be discussed on more detail later.
  • the CAMs of the modules will gradually fill with source addresses associated with ports or flags indicating that the source address is associated with another module and should not be handled in the same way as local ports.
  • a message is generated requesting a so-called ageing operation in orderto delete old addresses or addresses which have not been in use for a specified period of time.
  • the ageing operation can be under the control of a "master" module if one of the modules is deemed to be a "master” with all other as slaves. Alternatively it could recur when any one CAM is full and needs updating.
  • Each microprocessor then carries out an ageing out process in respect of its own CAM for all entries which are not flagged as permanent entries. However, instead of simply deleting old MAC addresses, the microprocessor records the MAC addresses of old entries prior to deletion from the CAM. It then forms a data packet with a list of MAC address entries which it has deleted locally and sends this list to each other microprocessor in the stack composed by modules interconnected by the local bus 11.
  • Each other microprocessor in the stack receives data packets from the other microprocessors during the ageing process and decodes and deletes those entries from its local CAM which it has been told by other microprocessors that it may delete. In this way, all addresses in all CAM's are kept up-to-date. All CAM's contain the same MAC addresses but the port numbers associated with the MAC addresses will differ depending on whether the address is on a port local to the particular CAM or not. The same will apply to the "permanent entry" flags.
  • box A is provided with a port 0 via which the rest of the network can be accessed. If a packet is received via port 0 of box A, the processor and CAM of box A will process the packet by examining the destination address for the packet.
  • the processor and CAM of box A can determine whether the destination address is one of the MAC addresses on the stack. If it is, then the packet will be sent to the appropriate port of box A i.e. to the actual port to which the device having the destination address is connected or to communications port 10 if the address is elsewhere in the stack.
  • the source address of this packet is not learned by any of the CAMs. If, however, the packet has a destination address which is not known to the CAM of box A, the packet is discarded or ignored in some convenient way. In our case, we prefer to send such a packet to a non existent port e.e. port 31.
  • the switch learns only source addresses associated with its own ports. It does not learn from destination addresses nor does it learn from the rest of the network.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

Un module de commutation pour ordinateur comporte un dispositif de mémoire destiné à mémoriser la relation entre les ports du commutateur et l'adresse de contrôle d'accès au support des dispositifs qui y sont connectés. Un port fait office de port de communication et tout paquet destiné à un dispositif non répertorié dans le dispositif de mémoire du commutateur est envoyé au port de communication. Un certain nombre de modules de commutation peuvent être connectés conjointement avec des données circulant entre des modules par l'intermédiaire de leurs ports de communication. Un de ces modules est muni d'un port de sortie à connecter au reste du réseau.
PCT/EP1996/002334 1995-05-31 1996-05-30 Systeme d'integrite reparti a memoire adressable par le contenu WO1996038958A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU59026/96A AU5902696A (en) 1995-05-31 1996-05-30 Distributed cam integrity system
GB9805471A GB2322055B (en) 1995-05-31 1996-05-30 Distributed CAM integrity system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9510930.2 1995-05-31
GBGB9510930.2A GB9510930D0 (en) 1995-05-31 1995-05-31 Distributed CAM integrity system

Publications (2)

Publication Number Publication Date
WO1996038958A2 true WO1996038958A2 (fr) 1996-12-05
WO1996038958A3 WO1996038958A3 (fr) 1997-01-09

Family

ID=10775241

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1996/002334 WO1996038958A2 (fr) 1995-05-31 1996-05-30 Systeme d'integrite reparti a memoire adressable par le contenu

Country Status (3)

Country Link
AU (1) AU5902696A (fr)
GB (2) GB9510930D0 (fr)
WO (1) WO1996038958A2 (fr)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4809362A (en) * 1987-03-13 1989-02-28 Center For Innovative Technology Fiber-optic star tree network
US5448565A (en) * 1992-11-12 1995-09-05 International Business Machines Corp. Multiport LAN bridge

Also Published As

Publication number Publication date
GB9510930D0 (en) 1995-07-26
GB9805471D0 (en) 1998-05-13
WO1996038958A3 (fr) 1997-01-09
AU5902696A (en) 1996-12-18
GB2322055A (en) 1998-08-12
GB2322055B (en) 2000-04-26

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